Light Fixture with Multimode Optical Output

ABSTRACT

A light fixture is provided with increased light output, uniformity of brightness and color and controlled lighting non-lambertian distributions by use of an optical element that functions simultaneously as an outcoupling TIR light guide and a direct throughput lens. It provides typical benefits of an edgelit light guide design including thin forms and shallow depth, extended emitting area, and single or dual peak off axis light distributions particularly useful in applications such as indirect illumination of ceilings, wall washing, aisle lighting, exterior façade lighting and area lighting as well as other lighting applications. Additionally, areas typically dedicated to bezels or edge reflectors can be greatly reduced or eliminated due to decreased hotspotting to provide a fixture face with very high percentage of light emitting area. Embodiments are described for direct, indirect, and direct indirect configurations.

RELATED APPLICATIONS

This application is a continuation in part of U.S. Non-ProvisionalUtility application Ser. No. 16/039,320 filed Jul. 18, 2018 which itselfclaims the benefit of U.S. provisional patent application Ser. No.62/534,187 titled “Lighting Subassembly With Dual Mode Optical Element”filed Jul. 18, 2017.

SUMMARY

Light fixture embodiments provide benefits of increased light output,uniformity of brightness and color by use of optical elements thatfunctions simultaneously as an outcoupling TIR light guide and a directthroughput lens. Provided are typical benefits of an edgelit light guidedesign including shallow depth, extended emitting area, and off axislight distributions such as batwing distributions particularly useful indownlighting and other lighting applications. Additionally, areadedicated to bezels or edge reflectors can be greatly reduced oreliminated due to decreased hotspotting to provide a fixture face withvery high percentage of light emitting area. Some embodiments can beconfigured as direct/indirect light fixtures.

BACKGROUND

Lighting systems incorporating optical waveguides positioned close tothe light source provide significant benefits such as thin form factorand adjustable lighting output. However, efficient optical coupling fromthe light source to the waveguide is difficult to achieve and typically10% to 30% of light is lost. Traditional approaches that target fulledge coupling of light into optical waveguides typically lose efficiencyby having low utilization of uncoupled light and of light that entersthe input edge but escapes light guide on a non-output face or near theedge where the output is blocked by a bezel or reflector. Often bezelsare deemed necessary to hide “hotspotting”, non-uniform brightness closeto light sources due to excessive outcoupling near the edge. Inaddition, light sources such as LEDs often have a variation of theircolor output over angle that are typically accentuated by coupling intooptical light guides.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1a is perspective view of a ceiling mounted light fixtureembodiment.

FIG. 1b is a perspective view of a suspended light fixture embodiment.

FIG. 2 is a cross section view of a light fixture with a conventionalplanar light guide.

FIGS. 3A and 3B (enlargement view) are cross section views of a lightfixture configured with an optical element having angled input edges andan overhang feature at the input edges.

FIG. 4 is a digital image of a Reference A light fixture representing aconventional edgelit light guide construction as shown in FIG. 2 butwithout a bezel or cover lens.

FIG. 5 is a digital image of Embodiment A light fixture shown in FIG. 3Aand FIG. 3B but without a bezel or cover lens.

FIG. 6 is a graph and table comparing quantitative metrics of Ref A vs.Embodiment A for characterizing brightness values along the line scanpaths for direct transmission shown in FIG. 4 and FIG. 5.

FIG. 7 is a graph and table comparing quantitative metrics of Ref A vs.Embodiment A for characterizing brightness values along the line pathsfor initial reflection shown in FIG. 4 and FIG. 5.

FIG. 8 is a polar plot of embodiment A with one side only LED strip onand the light fixture oriented down as a direct lit downlightingfixture.

FIG. 9 is a polar plot of embodiment A with LED strips on both sides onand the light fixture oriented down as a direct lit downlightingfixture.

FIG. 10 is a cross section detail view of an embodiment with two opticalelements configured to receive light from a central light sourcestructure.

FIG. 11 is a cross section detail view of an embodiment with two opticalelement input faces within a recessed cavity.

FIG. 12 is a cross section view of a light fixture embodiment having aninput face/output face alignment angle configured to direct asignificant portion of light out the opposing face to be subsequentlyreflected out the output face.

FIG. 13 is cross-section perspective view of a direct/indirect lightfixture embodiment with an x-y profile geometry linearly extruded in thez-axis to create a generally rectangular fixture shape

FIG. 14 is a cross-section perspective view of a direct/indirect lightfixture embodiment with the x-y profile geometry is rotated to produce agenerally circular shape fixture.

FIG. 15 is a cross-section view of a light fixture embodiment having 2input faces with differing input face/output face alignment angles.

FIG. 16 is a view of a direct/indirect light fixture embodiment.

FIG. 17 is a polar plot illustrating the light distribution of thedirect/indirect light fixture of FIG. 16.

FIG. 18 is a polar plot of the light distribution of the light fixtureembodiment of FIG. 16 reconfigured with to remove the apertures in thereflector and create an indirect only embodiment.

FIG. 19 is a table of data comparing the performance of differingconfigurations of the light fixture embodiment of FIG. 16.

FIG. 20A is a cross-section view of a cove light fixture embodiment.

FIG. 20B is a sketch of a photometric plot representing the lightdistribution from the cove light fixture embodiment of FIG. 20A.

FIG. 21A is a cross-section view of a wall wash light fixtureembodiment.

FIG. 21B is a sketch of a photometric plot representing the lightdistribution from the wall wash light fixture embodiment of FIG. 21A.

FIG. 22 is a cross-section view of a light fixture embodiment in which agasket is fitted between the housing and optical element overhang toprovide a seal with ingress protection.

DESCRIPTION

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing.

Embodiment configurations can be implemented in a wide range of lightfixtures. One such fixture that benefits from advantages in aestheticappearance, light distribution pattern, and luminous efficacy is shownin FIG. 1a The light fixture 100 a is mounted flush with ceiling tiles200 a in a ceiling in a direct lit downlighting application.Alternatively, FIG. 1b shows an embodiment suspended direct/indirectlight fixture 100 b which is mounted to hang below the ceiling 200 b andemit light out of both top and bottom output faces of the light fixture;in standard lighting industry terminology the downward light beingconsidered “direct” and the upward light illuminating the ceilingconsidered “indirect”. Typical light fixture embodiments include LEDs aslight sources and although the written descriptions may reference LED inthe singular, typically an array of LEDS is used and should be impliedif not explicitly stated or illustrated. Many types of reflectors may beused in various embodiments such as diffuse or specular reflectors orreflectors with surface features for redirection of incident light.Optical elements may contain surface features for purposes of lightoutcoupling, light redirection, or visual appearance. Arrays of featurescan be used such as a linear lenticular array which is often a suitablepattern.

For comparison with the embodiment A of FIG. 3, FIG. 2 shows across-section view of a lighting fixture having a conventional edge litlight guide. The housing 114 holds in place the LED board 102 with LED101, light guide 103, reflector 108, and cover lens 111. The light guide103 is a rectangular shaped sheet with an input face 104 and an outputface 105 that are adjacent faces oriented at a 90 degree angle. Bezels115A and 115B cover a significant portion of the ends of the light guidein order to hold the light guide and cover lens in place and also tomask hot spot non-uniformities near the input face of the light guide103.

FIG. 3A and FIG. 3B show a cross-section view of embodiment A lightingassembly in which LED 1 light sources are mounted on an LED board 2which providing a linear light source that inputs light into the opticalelement input face 4. Light propagates within the optical element 3 andis emitted from the output face 5. A portion of the light propagatesdirectly through the optical element 3 on the direct transmission path13 while concurrently a portion of the light propagates within theoptical element on a TIR path 12 until it outcouples from the opticalelement 3. Means for outcoupling light are provided by lenticularsurface 9 on the optical element opposing face 6 as well as by the lightscattering composition of the bulk optical element 3. In embodiment Athe light scattering composition is provided by polymer beads dispersedwithin an acrylic matrix material having a differing refractive index.Light outcoupling out the opposing face 5 is redirected toward theoptical element output face 5 by the reflector 8.

The optical element 3 is comprised of a light transmissive materialhaving a refractive index greater than the surrounding ambientenvironment; in the case of air >1. Optionally, regions of differingrefractive index may be dispersed within the volume to scatter light andcause a portion of light to out couple from the optical element.Embodiment A is comprised of PMMA acrylic matrix with PMMA beads ofdiffering refractive index dispersed throughout the volume. Otheralternative materials for an optical element include but are not limitedto clear or translucent grades of polycarbonate, cyclic olefincopolymers, silicone, and glass. PMMA acrylic has a refractive index ofapproximately 1.5 which in air produces a total internal reflection(TIR) critical angle of approximately 42 degrees. Dispersed lightscattering regions within the optical element can be achieved bydispersing materials of differing refractive index throughout thematerial. Alternatively, 2^(nd) phase regions can be formed in-situduring processing of immiscible material blends.

The housing 14 encloses and holds in place optical components includingthe optical element 3, LED board 2, and if optionally present, the coverlens 11. The housing contains a bezel 15 feature which functions tocover the edge of the optical element including some or all of theoptical element overhang 7.

The optical element input face 4 is inset from the outer perimeter ofthe optical element output face 5 and is angled so as to form an acuteinput/output face alignment angle 10, the angle being 70 degrees in thespecific case of embodiment A. The acute input/output alignment anglefunctions to reduce “headlamp” type hot spots from the reflector 8 nearthe input face 4 and also increases the ratio of direct transmission toTIR light propagating within the optical element. The optical elementoverhang 7 provides a feature for mechanically securing the opticalelement in the housing 14 without excessively trapping light behind thebezel 15 as typically occurs in a conventional edge lit constructionsuch as with the bezels 115A and 115B and input face 104 of FIG. 2. Thisfunctions to improve overall efficacy (lumens per watt) of the lightingsystem.

The cover lens 11 is an optional component which can be configured toenclose the output face of the light fixture and provide an appearancemore uniform in brightness and color. Adjustments to the cover lens 11surface geometry and bulk light scattering properties can be used tomodify the output light distribution from that originating from theoptical element output face 5. For example, adjustments to cover lenssurface or volumetric light redirecting properties can be used todecrease the wide angle degree of lobes in the light distributionpattern or make brightness or color variations in the beam patternemitting from the optical element output face more uniform. In thespecific case of embodiment A, the surface is congruent with the shapeof the cover lens and the bulk of the cover lens material has lightscattering properties measured to have a symmetrical full width halfmaximum value of 68 when measured as a separate component on measurementequipment using as an input light source a narrow beam laser normal tothe input surface.

FIG. 4 is a digital image of a Reference A light fixture representing aconventional edgelit light guide construction as shown in FIG. 2 butwithout a bezel or cover lens. FIG. 5 is a digital image of Embodiment Alight fixture shown in FIG. 3A and FIG. 3B but without a bezel or coverlens. Both images were taken at a 45 degree viewing angle of the outputface. Marked on the images are locations where line scans were analyzedto assess brightness levels corresponding to light directly transmittedthrough the light guide/optical element and light that does an initialreflection from the reflector near the input face. In the case ReferenceA, the initial reflection produces significant hot spot patterningcommonly referred to as “headlamping” due to similarity in appearance ofautomotive headlamps projecting onto ground in front of a car. Theheadlamping effect is negligible in the FIG. 5 image of embodiment A.

FIG. 6 and FIG. 7 each show graphs and quantitative metricscharacterizing brightness values along the line scan paths; FIG. 6 fordirect transmission and FIG. 7 for initial reflection. For embodiment A,the direct transmission is significantly greater than reference A. Inaddition to the data of FIG. 6, this is evidenced by illuminationmeasurements at 45 degrees comparing full optical light guide/opticalelement output vs. that with the output face masked except for thenarrow band of direct transmission zone near the input edge. In thiscase, embodiment A direct transmission was 28% of full output at 45degree angle while reference A direct transmission was 12% of totaloutput at 45 degree angle.

FIG. 8 is a polar plot of embodiment A with one side only LED strip onand the light fixture oriented downward as a direct lit downlightingfixture. The cover lens is embodiment A is a diffusion lenscharacterized by a goniometric radiometer as having a symmetric FWHM of68. This provides a large amount of light scattering that decreases theoff axis orientation of light emitted from the optical element outputface and produces a light distribution closer to lambertian. The amountof asymmetry in light distribution output can be controlled by selectionof amount of light scattering in the cover lens to obtain a range ofoptions between the “no cover lens” and “with cover lens” optionsillustrated in FIG. 9.

FIG. 9 is polar plot of embodiment A with LED strips on both sides of anoptical element and the light fixture is oriented down as a direct litdownlighting fixture and shows a batwing type light distribution whichcan be adjusted to provide less asymmetry by increasing light scatteringin the cover lens. The cover lens in embodiment A has a symmetric FHWMof 6868 which results in a very symmetric light distribution.

FIG. 10 is a cross section detail view of an embodiment with two opticalelements configured to receive light from a central light sourcestructure. Two LED boards 1002, are positioned upon a central lightsource mount 1016 to emit light from LEDs 1001 in opposing orientationsinto optical elements 1003, the result being a batwing type light outputfrom the light fixture. The central light source mount also serves as amounting ledge for the optical element overhang 1007 and also a bezel tomask from view the edge of the optical element, thereby appearing theuniformity appearance.

FIG. 11 is a cross section detail view of an embodiment with two opticalelement input faces 1104 positioned within a recessed cavity 1117. Twooptical elements 1103 are configured to receive light from a centrallight source structure. Two LED boards 1102, are positioned upon acentral light source mount 1116 to emit light from LEDs 1101 in opposingorientations, the result being a batwing type light output from thelight fixture. The central light source mount also serves as a mountingledge for the optical element overhang 1007 and also optionally a bezel1115 to mask from view the edge of the optical element, therebyappearing the uniformity appearance. A cover lens 1111 may also beoptionally positioned to further enclose the fixture and/or adjust lightdistribution or appearance.

FIG. 12 is a cross section view of a light fixture embodiment having anoptical element input/output face alignment angle 1210 configured todirect a significant portion of direct transmission light 1213 out theoptical element opposing face 1206 to be subsequently reflected off thereflector 1208 and back through the optical element 1203 and out theoutput face 1205. The light redirecting features 1209 on the output face1205 function to redirect the optical path.

FIG. 13 is cross-section perspective view of a direct/indirect lightfixture embodiment with an x-y profile geometry linearly extruded in thez-axis to create a generally rectangular fixture shape. Light from theLED 1301 on the LED board 1302 is received by the optical element inputface 1304 of the optical element 1303 and propagates along a directtransmission path 1313, as illustrated by a single example light ray,and exits the optical element through optical element output face 1305 athen proceeds to transmit through the cover lens 1311 a resulting inupward light distribution which becomes part of the indirect lightoutput of the fixture. The optical element 1303 contains lightscattering regions which cause some portion of light to scatter enoughto exceed the critical total internal reflection angle to outcouple outone of the two optical element output faces 1305 a and 1305 b and thensubsequently through a cover lens 1311 a or 1311 b. In this embodimentlight propagating out the bottom lens cover 1311 b is considered directlight fixture output while light propagating out the lens cover 1311 ais considered indirect light fixture output.

FIG. 14 is a cross-section perspective view of a direct/indirect lightfixture embodiment with the x-y profile geometry is rotated to produce agenerally circular shape fixture. Light from the LED 1401 on the LEDboard 1402 is received by the optical element input face 1404 of theoptical element 1403 and propagates along a direct transmission path1413, as illustrated by a single example light ray, and exits theoptical element through optical element output face 1405 a then proceedsto transmit through the cover lens 1411 a resulting in upward lightdistribution which becomes part of the indirect light output of thefixture. The optical element 1403 contains light scattering regionswhich cause some portion of light to scatter enough to exceed thecritical total internal reflection angle to outcouple out one of the twooptical element output faces 1405 a and 1305 b and then subsequentlythrough a cover lens 1411 a or 1411 b. In this embodiment lightpropagating out the bottom lens cover 1411 b is considered direct lightfixture output while light propagating out the lens cover 1411 a isconsidered indirect light fixture output. The circular geometry enablessome novel light distributions. In particular, elliptical (includingcircular) light distributions can be achieved. Typically the inputface/output face alignment angle will be rotated 360 degrees which willbe contribute to a circular light distribution. Variations in cover lenslight redirecting features can contribute to more elliptical lightdistributions; for example, if there are an array of linear lenticularfeatures the features will direct light differently at differing inputangles.

FIG. 15 is a cross-section perspective view of a direct/ indirect lightfixture embodiment having 2 input faces with differing optical elementinput face/output face alignment angles. Optical element input face 1504a and optical element output face 1505 b create a 90 degree opticalelement input face/output face alignment angle 1510 a. In contrast,optical element input face 1504 b and optical element output face 1505 bcreate an optical element input face/output face alignment angle 1510 bof 110 degree which produces an optical element that projects more lightout optical element output face 1505 a and cover lens 15111 a in anupward indirect direction of the light fixture than through the downwarddirect light fixture direction wherein light escapes the optical element1503 through the optical element output face 1505 b and subsequentlythrough the cover lens 1511 b. Each input face of the optical element isaligned with an LED board 1501 with LED 1502 and with each LED boardmounted onto a housing 1514.

FIG. 16 is a cross-section perspective view of a direct/indirect lightfixture embodiment with light input into two sides of the light fixture.The two sides are mirror images of each other so the followingdescription applies to light input into the optical embodiment from bothsides. Light from the LED 1601 on the LED board 1602 is received by theoptical element input face 1604 of the optical element 1303 andpropagates along a direct transmission path 1613, as illustrated by asingle example light ray, and exits the optical element through opticalelement output face 1605 a resulting in upward light distribution whichbecomes part of the indirect light output 1619 of the fixture. Theoptical element 1603 contains light scattering regions which cause someportion of light to scatter enough to exceed the critical total internalreflection angle to outcouple out one of the two optical element outputfaces 1605 a and 1605 b. The housing 1614 contains apertures 1620 on thebottom of the fixture which are openings in both the housing 1614 andreflector 1608 through which a portion of the total light output istransmitted. In this embodiment light propagating out the bottom of thefixture is considered direct light fixture output 1618 while lightpropagating upward is considered indirect light fixture output 1619.Alternative embodiments may contain a cover lens over the top or bottomof the fixture to enclose and/or further direct light to further adjustlight distribution or visual appearance.

FIG. 17 is a polar plot illustrating the measured light distribution ofthe direct/indirect light fixture embodiment of FIG. 16. Both indirect(upwards) and direct (downwards) light distributions are of asymmetrical batwing type useful for even illumination when projectedonto flat target illumination surfaces such as ceiling, floors, andtable tops. 14% of light is downward direct light fixture output and 86%is upward indirect light fixture output. Asymmetric embodiments areeasily configured by adjusting to differ the amount of electrical powerthe power applied to the two using only a LED board on a single side ofthe optical element.

FIG. 18 is a polar plot of the measured light distribution of a lightfixture embodiment of FIG. 16 reconfigured to remove the apertures inthe reflector and create an indirect only embodiment. In thisembodiment, the reflector 1608 does not have apertures but ratherextends to cover the entire bottom side of the optical element.

FIG. 19 is a table of data comparing the performance of differingconfigurations of the light fixture embodiment of FIG. 16 and summarizesoptical performance of high efficacy, light distribution, and a highratio of indirect to direct light fixture output.

FIG. 20A is a cross-section view of a wall wash light fixtureembodiment. An optical element 2003 receives light from an LED 2001mounted on an LED board 2002 at an optical element input face 2004. TheLED board 2002 is mounted within the housing 2014 and has on theopposite side from the LED an electrical connector 2021. The backsideplacement of the electrical connector allows the frontside with LED tomaintain a flat plane for mounting flush to the housing. Light enteringthe optical element 2003 at the input face 2004 propagates through theoptical element by a combination of direct transmission and TIR pathsbefore outcoupling out the optical element output face 2005. Light thatexits the light guide from the optical element opposing face 2006reflects off the reflector 2008 and propagates back through opticalelement to exit out the output face 2005. The wedge shape of the opticalelement 2003 improves efficacy and uniformity by gradually decreasingthe cross-sectional area available for TIR.

FIG. 20B is a sketch of a photometric plot representing the lightdistribution from the cove light fixture embodiment of FIG. 20A. Theasymmetric light distribution is well suited for a cove lightingapplication wherein the light fixture is typically mounted horizontallynear a wall/ceiling interface.

FIG. 21A is a cross-section view of a wall wash fixture embodiment. Anoptical element 2003 receives light from an LED 2101 mounted on an LEDboard 2102 at an optical element input face 2104. The LED board 2102 ismounted within the housing 2114 and has on the opposite side from theLED an electrical connector 2021. The backside placement of theelectrical connector allows the frontside with LED to maintain a flatplane for mounting flush to the housing. Light entering the opticalelement 2103 at the input face 2104 propagates through the opticalelement by a combination of direct transmission and TIR paths beforeoutcoupling out the optical element output face 2105. Light that exitsthe light guide from the optical element opposing face 2106 reflects offthe reflector 2108 and propagates back through optical element to exitout the output face 2105. The wedge shape of the optical element 2103improves efficacy and uniformity by gradually decreasing thecross-sectional area available for TIR.

FIG. 21B is a sketch of a photometric plot representing the lightdistribution from the wall wash light fixture embodiment of FIG. 21A.The asymmetric light distribution is well suited for a wall washapplication wherein the light fixture is typically mounted verticallywith the optical element output face substantially parallel to a wallsurface.

FIG. 22 is a cross-section view of a light fixture embodiment in which agasket is fitted between the housing and optical element overhang toprovide a seal with ingress protection. The location of the gasket setback from the LED board minimizes blockage of light output from theoutput face and can be an advantage in both efficacy and visualappearance.

What is claimed is:
 1. A light fixture comprising; a) an first opticalelement having an input face perpendicular to a x-y profilecross-section, an output face perpendicular to a x-y profilecross-section, and an optical element overhang which extends beyond theinput face; b) a first light source aligned perpendicular to the z axisof the optical element which emits light into the input face of thelight guide; wherein a portion of light is directly transmitted from theinput face through the output face and a portion of light is propagatedwithin the optical element by total internal reflection at output face.2. The light fixture of claim 1 having an input face and an output facearranged with an input face/output face alignment angle substantiallyless than 90 degrees within a x-y cross-sectional plane aligned with theoptical output axis of a light source aligned perpendicular to the zaxis of the optical element which emits light into the input face of theoptical element;
 3. The light fixture of claim 1 further comprising asecond optical element joined to the first optical element by means ofthe optical overhang.
 4. The light fixture of claim 1 further comprisinga second optical element and second light source positioned as a mirrorimage of the first optical element and first light source.
 5. The lightfixture of claim 4 further comprising a cover panel positioned adjacentto the junction between the first and second optical elements.
 6. Thelight fixture of claim 1 wherein the light fixture of claim 1 whereinthe 3 dimensional shape of the optical element is a x-y cross-sectionalprofile extended linearly into a z axis.
 7. The light fixture of claim 1wherein the light fixture of claim 1 wherein the 3 dimensional shape ofthe optical element is a x-y cross-sectional profile extendedrotationally into a z axis to produce an elliptical geometry.
 8. Thelight fixture of claim 1 further comprising a second light sourcealigned perpendicular to the z axis of the optical element which emitslight into a second input face of the light guide.
 9. The light fixtureof claim 2 wherein the input/output face alignment angle preferentiallydirects more light to a first output surface and less light to a secondoutput surface.
 10. The light fixture claim 1 further comprising areflector mounted adjacent to an optical element face opposing an outputface.
 11. The light fixture of claim 10 further comprising one or moreapertures in the reflector to enable a direct/indirect lightdistribution.
 12. The light fixture of claim 1 further havingdirect/indirect light fixture output.
 13. The light fixture of claim 1wherein the optical element is a wedge shape.
 14. The light fixture ofclaim 1 configured for a cove lighting application.
 15. The lightfixture of claim 1 configured for a wall washing application.